Jaime goes undercover with a deadly human trafficking ring. Danny and Baez investigate a homicide connected to Darryl Reid, Danny's old partner. Also, Frank grapples with whether to publicly support Mayor Chase on a policy decision and Eddie is determined to teach a young shoplifter a lesson.

Danny and Baez join forces with Danny’s old partner, Jackie Curatola, when a serial killer reappears. Also, Eddie faces backlash when she tries to help a woman who accuses a sergeant of rape. Meanwhile, Jamie clashes with his nephew, Joe Hill, when Joe interferes with Jamie’s undercover operation and Frank is blindsided when Mayor Chase publicly suggests bringing back a Commission of Police.

Frank grapples with the personal loss of his best friend and how best to help Tess Ross, the daughter of his best friend, when she lands in jail; Jaime and his nephew, Joe Hill, race against the clock to reunite a trafficking victim with her sister.

Danny reunites with a troublesome teenager from a past case when the youth finds herself in danger. Also, Frank faces a difficult personnel decision close to home. Meanwhile, Jamie grows suspicious when Henry is asked to be interviewed for an investigative web series and Erin and Anthony investigate when Erin is the alleged target of a shooting.

Erin is designated to lead a federal investigation into corrupt horse racing. Also, Jamie investigates a drug trafficking operation involving rival gangs. Meanwhile, Danny and Baez look into a series of assaults in Little Vietnam with the help of a familiar face and Frank is torn when he learns the Brotherhood of Teamsters are lobbying for NYPD officers to join their union.

Danny and Baez investigate a homicide involving voodoo with the help of Baez's old partner. Also, Eddie and a fellow officer team up with Captain McNichols when they suspect a prestigious school is employing discriminatory admission practices. Meanwhile, Erin is confronted by a middle-schooler who claims Erin sent her brother to prison and Frank tries to help Garrett's neighbor when her car is held as police evidence.

Danny gets involved when Sean becomes the latest victim in a series of robberies on Sean's college campus. Also, Erin grows suspicious of an overworked attorney who she believes isn't acting in his client's best interest; Eddie and her partner, Badillo, investigate an apartment burglary in which the tenants suspect their landlord; and Frank is livid when he learns Jamie and his grandson, Joe Hill, were in a physical altercation in public.

Danny and Gormley race to find Gus Vanderlip, a committed detective who is dangerously determined to uncover how a rapist he arrested is back on the streets; on the eve of their anniversary, Jamie and Eddie are sent on an undercover assignment to expose a corrupt sober living house; and Henry asks Frank for a favor regarding the NYPD's 9/11 Victims Compensation Fund